1. Field of the Invention
The present invention relates to an improved method of cleaning and removing the products of corrosion, oxidation and sedimentation which occur within and become attached to the walls of the interior heat exchanger tubes which are located within a pressure vessel such as a tube bundle heat exchanger, boiler, condenser, or the like, through utilization of a repetitive shock wave induced into a liquid which is placed within the tubes and then subsequently flushing the tubes. The shock wave serves to effectively and safely loosen the products of corrosion, oxidation and sedimentation which are located within or settle on the walls of the interior of the heat exchanger tubes, and thereby facilitates their easy removel through flushing and vacuuming the vessel. The concept of utilizing a repetitive pressure pulse shock wave to remove the buildup of sedimentation or "sludge" which accumulates in the bottom of a heat exchanger vessel around the exterior of the heat exchanger tubes is described in presently pending patent application Ser. No. 486,352, filed 4/19/83 and entitled "Method of Pressure Pulse Cleaning A Tube Bundle Heat Exchanger". The inventors of the invention in that patent application, Terry D. Scharton and G. Bruce Taylor, are the same inventors of the invention in the present patent application.
2. Description of the Prior Art
One of the major components of a heat exchanger are a large number of individual tubes which have fluid circulating through them. These heat exchangers or steam generators have experienced many problems due to the buildup of products of corrosion, oxidation, sedimentation and comprable chemical reactions within the heat exchanger.
The problem of removing the products of corrosion, oxidation and sedimentation in various locations on the outside of the tubes have been discussed in the following prior art patents:
1. U.S. Pat. No. 2,664,274 issued to Worn, et al.; PA1 2. U.S. Pat. No. 2,987,086 issued to Branson; PA1 3. U.S. Pat. No. 3,033,710 issued to Hightower, et al.; PA1 4. U.S. Pat. No. 3,240,063 issued to Sasaki, et al.; PA1 5. U.S. Pat. No. 3,295,596 issued to Ostrofsky, et al.; PA1 6. U.S. Pat. No. 3,433,669 issued to Kouril; PA1 7. U.S. Pat. No. 3,428,811 issued to Harriman, et al.; PA1 8. U.S. Pat. No. 3,447,965 issued to Teumac, et al.; PA1 9. U.S. Pat. No. 3,854,996 issued to Frost, et al.; PA1 10. U.S. Pat. No. 4,120,699 issued to Kennedy, et al.; PA1 11. U.S. Pat. No. 4,167,424 issued to Jubenville, et al.; PA1 12. U.S. Pat. No. 4,320,528 issued to Scharton & Taylor. PA1 1. Application Ser. No. 370,826 filed 4/22/82 by Scharton and Nikolchev for "Deep Crevice Ultrasonic Cleaner". PA1 2. Chemical Cleaning of BWR and Steam Water system at Dresdent Nuc. Pw. Station, Obrecht et al., pp 1-18 (10/26/60) 21st Ann. Conf. of Eng. PA1 3. Special Tech. Pub. 42 (1962) ASTM Role of Cavitation in Sonic Energy Cleaning, by Bulat. PA1 4. R&D Status Report Nuclear Power Division, which appeared on pages 52 through 54 of the April 1981 issue of the EPRI Journal. The article was by John J. Taylor.
They are also discussed in the following pending patent application and prior art literature:
All of the above referenced patents have been extensively discussed in both U.S. Pat. No. 4,320,528 or else in presently pending U.S. patent application Ser. No. 370,826 filed on 4/22/82. The following two prior art publications have also been discussed in these references.
All of the prior art discussed above employs the use of ultrasonics. While the methods discussed in the prior art, especially those in U.S. Pat. No. 4,320,528 and application Ser. No. 370,826 are very effective and valuable, the requirement of using ultrasonics has several significant disadvantages. First, in order to generate the ultrasonic waves, expensive transduces must be used. This requires considerable effort and expense to bring the ultrasonic transducers to the site of the heat exchanger and then putting them in their proper place in the location of the heat exchanger. Second, in order to achieve an effective level of ultrasonic waves, it is often necessary to cut away a portion of the heat exchanger wall and put the face of the transducer at the location of the cut away portion. Many owners of the heat exhanger are very reluctant to have a portion of the wall cut away and then later welded back in place after the heat exchanger has been cleaned.
A third problem which arises with prior art applications is the use of corrosive chemicals to assist in the cleaning operation. While the chemicals servce to clean and remove the undesirable elements, they also serve to eat away at the various components of the heat exchanger. Therefore, it is desirable to find a method of cleaning which does not require the use of corrosive chemicals.
The method of pressure pulse cleaning described in presently pending U.S. patent application Ser. No. 468,352 by inventors Scharton and Taylor discusses the use of pressure pulse cleaning on the outside of the heat exchanger tubes and primarily adjacent the lower tube support sheet. None of the prior art references cited disclose or teach a method of pressure pulse cleaning the inside of the heat exchanger tubes.